The present invention relates to coated formed metal objects such as corrugated steel pipe containing either outer coatings, inner coatings, or both outer and inner coatings of protective substances such as asphalt or cementitious coatings, building panels or roofing panels similarly shaped or formed and coated as well as machine housings or equipment casings having sound proofing or abrasion resistant or corrosion resistant coatings applied thereto. More particularly, the present invention relates to such previously described structures, referred to hereinafter as "formed metal structures", having improved integrity between the surface coatings applied thereto and the underlying metallic substrates.
In U.S. Pat. No. 4,192,697, a method for forming an adherent protective coating on articles, particularly pipes, comprising wrapping the pipe with a hot impregnated fabric strip, preferably a glass fiber strip impregnated with hot, molten adhesive and over-wrapping the same with a polyvinyl chloride sheet is disclosed.
In U.S. Pat. No. 4,158,371, a coating composition providing good crack resistance comprising 50 to 70 weight percent of a mineral aggregate, about 15 to 35 weight percent of finely divided mineral filler, about 5 to 20 weight percent asphalt and about 0.05 to 7 weight percent of a rubbery radial teleblock copolymer, about 0 to 7 percent of an oil and about 0 to 0.5 weight percent of a fibrous material is disclosed. The composition may be applied in a molten state to a substrate such as a steel pipe after first priming the surface thereof with an asphalt composition.
In Japanese Publication J 59-083,616, an asphalt coating sheet comprising a heat resistant vinylon cloth laminated with blown asphalt is disclosed for wrapping about steel pipes. A similar bitumen based tape is disclosed in East German laid open publication DL-139,634, wherein glass fiber is impregnated and coated on both sides with a bitumen composition and one side thereof is further coated with an adhesive while the other side is coated with a polyethylene film. The tape is then applied to structural steel components to protect against corrosion.
In DT 2,829,387, a thermoplastic coated, lining material comprising a base layer of a woven or knitted fabric, a thermoplastic layer on one side and a fiber pile layer on the opposite side is disclosed. The fiber pile surface is employed for attaching a reinforcing material such as concrete.
The above described previously known processes for providing protective coatings to formed metal articles have proven deficient for one or more reasons. In general, attempting to apply a tape or fabric to a already formed metal article is extremely limited in practice. Only articles of generally a smooth uniform surface such as round pipes may be satisfactorily coated employing preformed tapes. Odd shaped objects, metal objects having corners or edges, and the internal surfaces of formed metal objects often cannot be coated or adequately protected by this or other previously known techniques.
Moreover, the adhesive bond between a metal surface and in particular, a bitumen or asphalt based adhesive has been found to be insufficient to provide satisfactory long term adhesion.
It would be desirable to provide coated metal objects having improved adhesion between the metal surface and the coating applied thereto.
It would further be desirable to provide coated metal articles having any desired shape or form, and when defining both internal or external surfaces, casted on either or both of such surfaces. Finally, it would be desirable to provide an improved method for providing bitumen or asphalt coated formed metal objects.